voicemail

My friend has a Note 13. Every time I call him, it rings once(both my end and his), then goes straight to voicemail. any suggestions ???

Hello, i am sure I managed to do this on other androids but on my Note 6 Pro with miui10 if I go into 'voicemal' settings i can select the default number to dial for voicemail but i cannot see where I can change the notification tone to one I want. only vibrate 'on or off' How can I change...